Funding is requested to support the ourchase of a Coulter Elite Flow cytometry system to replace out-dated instrumentation that currently services 45 investigators (including members of the NIH-supported University of Michigan Cancer Center and Multi-purpose Arthritis Center) on the Medical Center Campus. Because of increased demand for newer flow cytometry applications and greater efficiency of cytometer operation and data analysis, the current Coulter EPICS C instrumentation (purchased in 1984) is no longer meeting the needs of the users. What is now required is a flow cytometry system that can perform the following extended applications: (a) three and four color fluorescence, (b) dual laser excitation, (c) DNA cell cycle analysis with two surface labels and doublet discrimination, (d) fluorescence versus time histograms, (e) expanded fluorescence scale, (f) list mode data collection and analysis, and (g) the potential for chromosome analysis/sorting. The Coulter Elite system is capable of providing these new services in addition to the more routine flow cytometry applications (single and dual parameter analysis and sorting) performed by the single laser EPICS C instrument. Justification for the proposed instrumentation is documented in the project descriptions of 19 major flow cytometry users. Letters of institutional support from the directors of the Cancer Center (Dr. Wicha), Arthritis Center (Dr. Palella), the Associate Dean for Research (Dr. Goldstein), as well as the director of Human Gene Therapy Initiative/Genome Mapping Project (Dr. Collins) are provided. The operating costs of the current Flow Cytometry Laboratory and the proposed new (replacement) instrumentation will be shared by NIH Core Grants from the Cancer and Arthritis Centers as supplemented by a users fee.